The 60" iPF 9000 originally came with the PF-01 printheads but can be upgraded to the PF-03 printheads. The PF-02 and PF-03 printheads have design improvements including a teflon-like coating to prevent clogging and are compatible with any x000 printer that came with a PF-01 printhead. So yes, if you are wanting to put a 5100 printhead in a 9000, you can do that easily. When I've done that I've seen a slight change in the grey balance so you might consider re-profiling afterwards.